Prospect of rabi crops in South-West coastal area under climate change scenarios

Abstract

In the south-west coastal zone of Bangladesh, frequent natural disasters like flood, cyclone and associated storm surge, waterlogging, river erosion, etc., are familiar phenomena. Super cyclones like Sidr (2007) and Aila (2009) increased the soil and water salinity that hampered agriculture, the major livelihood option. But recently, salinity has reduced and local farmers have introduced some dry season cash crops like sunflower, sesame, watermelon, etc., along with boro rice cultivation in a small scale. This study has been conducted to assess the prospect of dry season crops under potential future climate in Polder 31 in Dacope upazila of Khulna district, in the south-west coastal zone. Participatory Rural Appraisal tools like Focus Group Discussions, Key Informant Interviews, semi-structured individual interviews, field observations and measurements, technical analyses, satellite images, mapping tools and a crop model named FAO AquaCrop were used in this study. Information about historical key events and previous and present agricultural practices was obtained and analyzed using timeline analysis to determine the trend in agricultural practices while information about local canals was collected to evaluate the storage capacity after re-excavation. Impacts of climate change on boro rice and sunflower were assessed for the years 2015-2050 using the AquaCrop model. Primary and secondary data were collected from several field visits to the study area and relevant organizations including Bangladesh Meteorological Department, Bangladesh Water Development Board and Soil Resource Development Institute. For calibration and validation of the model, an experimental study was conducted with Binadhan-8 rice and Hysun 33 sunflower during the dry season of 2014. From seeding to harvesting stages, necessary data on crop canopy cover, duration of flowering, soil texture and salinity, irrigation water quality and schedules, crop yields and biomasses were collected through field measurements and monitoring. Future climatic data were available from the PRECIS model outputs for three ensemble scenarios, QUMP-00, QUMP-08 and QUMP-16, of IPCC-SRES scenario A1B from the Met Office, Hadley Centre, UK. Bias correction of future climate data was performed using the delta change method. The timeline analysis of historical events showed that, though the practice of shrimp cultivation in Polder 31 reached to full scale in 1992 due to its high profit margin, but with time the damaging aspects of shrimp cultivation were observed and people abandoned this practice from 2008. At present, perception of local people has changed and they have switched back to crop agriculture for better standard of living. The presently silted up canals have a good potential to store freshwater for irrigation and if the water can be utilized to cultivate boro rice and rabi crops then the irrigation coverage and profit will be of considerable amount. The observed and AquaCrop model simulated yields of rice were 5.30 and 5.33 t/ha and of sunflower were 1.20 and 1.25 t/ha respectively which indicate good performance of this model during calibration and validation. Using bias corrected future climate data, predicted yields of rice and sunflower were obtained which showed increasing trends. This indicates good future potential of dry season crops under proper management practices and this knowledge may encourage the local farmers to invest in the dry season crops. This also demonstrates that, integrated practice of cultivating both staple food and cash crops with improved irrigation water storage facilities can improve income and serve as the way to attain food security in the long run.